Photosynthetic Ability Research Articles

Woody species with higher hydraulic efficiency or lower photosynthetic capacity discriminate more against 13C at the global scale

Leaf carbon isotope composition (δ13C) provides an integrative record on the carbon and water balance of plants over long periods. Photosynthetic ability and hydraulic traits which are highly associated with stomatal behavior could affect leaf δ13C. Association between photosynthetic ability and leaf δ13C has been examined, however, how hydraulic traits influence leaf δ13C has not been fully understood. To fill this gap, we investigated the variations in leaf δ13C among 2591 woody species (547 shrub and 2044 tree species), and analyzed the link of leaf δ13C with leaf photosynthetic and xylem hydraulic traits. Our result showed that leaf δ13C was positively correlated to leaf photosynthetic ability and capacity. For hydraulic traits, leaf δ13C was negatively related to hydraulic conductivity (Ks), xylem pressure inducing 50 % loss of hydraulic conductivity (P50) and vessel diameter (Vdia). Associations of leaf δ13C with xylem hydraulic traits indicate woody species with stronger hydraulic safety discriminated less against 13C, while woody species with higher hydraulic efficiency had more negative leaf δ13C. Shrub species, which showed a lower Vdia and P50, had a significant less negative leaf δ13C than tree species. Furthermore, woody species inhabiting in dry regions discriminated less against 13C than those growing in humid regions. Moreover, leaf δ13C displayed a low phylogenetic signal based on Blomberg's K statistic. Overall, woody species with a higher leaf photosynthetic ability or stronger hydraulic safety system discriminated less against 13C and adopt the provident water use strategy.

Globally distributed Myxococcota with photosynthesis gene clusters illuminate the origin and evolution of a potentially chimeric lifestyle

Photosynthesis is a fundamental biogeochemical process, thought to be restricted to a few bacterial and eukaryotic phyla. However, understanding the origin and evolution of phototrophic organisms can be impeded and biased by the difficulties of cultivation. Here, we analyzed metagenomic datasets and found potential photosynthetic abilities encoded in the genomes of uncultivated bacteria within the phylum Myxococcota. A putative photosynthesis gene cluster encoding a type-II reaction center appears in at least six Myxococcota families from three classes, suggesting vertical inheritance of these genes from an early common ancestor, with multiple independent losses in other lineages. Analysis of metatranscriptomic datasets indicate that the putative myxococcotal photosynthesis genes are actively expressed in various natural environments. Furthermore, heterologous expression of myxococcotal pigment biosynthesis genes in a purple bacterium supports that the genes can drive photosynthetic processes. Given that predatory abilities are thought to be widespread across Myxococcota, our results suggest the intriguing possibility of a chimeric lifestyle (combining predatory and photosynthetic abilities) in members of this phylum.

Panicle transcriptome of high-yield mutant indica rice reveals physiological mechanisms and novel candidate regulatory genes for yield under reproductive stage drought stress

BackgroundReproductive stage drought stress (RDS) is a major global threat to rice production. Due to climate change, water scarcity is becoming an increasingly common phenomenon in major rice-growing areas worldwide. Understanding RDS mechanisms will allow candidate gene identification to generate novel rice genotypes tolerant to RDS.ResultsTo generate novel rice genotypes that can sustain yield under RDS, we performed gamma-irradiation mediated mutation breeding in the drought stress susceptible mega rice variety, MTU1010. One of the mutant MM11 (MTU1010 derived mutant11) shows consistently increased performance in yield-related traits under field conditions consecutively for four generations. In addition, compared to MTU1010, the yield of MM11 is sustained in prolonged drought imposed during the reproductive stage under field and in pot culture conditions. A comparative emerged panicle transcriptome analysis of the MTU1010 and MM11 suggested metabolic adjustment, enhanced photosynthetic ability, and hormone interplay in regulating yield under drought responses during emerged panicle development. Regulatory network analysis revealed few putative significant transcription factor (TF)-target interactions involved in integrated signalling between panicle development, yield and drought stress.ConclusionsA gamma-irradiate rice mutant MM11 was identified by mutation breeding, and it showed higher potential to sustain yield under reproductive stage drought stress in field and pot culture conditions. Further, a comparative panicle transcriptome revealed significant biological processes and molecular regulators involved in emerged panicle development, yield and drought stress integration. The study extends our understanding of the physiological mechanisms and candidate genes involved in sustaining yield under drought stress.

A cryptic radiation of Caribbean sea slugs revealed by integrative analysis: Cyerce 'antillensis' (Sacoglossa: Caliphyllidae) is six distinct species.

Integrative studies have revealed cryptic radiations in several Caribbean lineages of heterobranch sea slugs, raising questions about the evolutionary mechanisms that promote speciation within the tropical Western Atlantic. Cyerce Bergh, 1871 is a genus comprising 12 named species in the family Caliphyllidae that lack the photosynthetic ability of other sacoglossans but are noted for vibrant colours on the large cerata (dorsal leaf-like appendages) that characterize many species. Two species are widely reported from the Caribbean: Cyerce cristallina (Trinchese, 1881) and Cyerce antillensis Engel, 1927. Here, we present an integrative assessment of diversity in Caribbean Cyerce. Four methods of molecular species delimitation supported seven species in samples from the Caribbean and adjacent subtropical Western Atlantic. Six delimited species formed a monophyletic lineage in phylogenetic analyses but were > 9% divergent at the barcoding COI locus and could be differentiated using ecological, reproductive and/or morphological traits. We redescribe C. antillensis, a senior synonym for the poorly known Cyerce habanensis Ortea & Templado, 1988, and describe five new species. Evolutionary shifts in algal host use, penial armature and larval life history might have acted synergistically to promote the rapid divergence of endemic species with restricted distributions in this radiation, substantially increasing global diversity of the genus.

Effects of Exogenous Plant Hormone Spraying on the Phytoremediation by Bidens pilosa L. in Cadmium-contaminated Soil

To explore the effect of exogenous plant hormone spraying on the absorption of heavy metals by hyperaccumulated plants, Bidens pilosa L. was selected as the tested plant owing to the large biomass, short growth cycle, and high accumulation efficiency. Here, the effect of foliar spraying 6-benzylaminopurine (6-BA), salicylic acid (SA), and 24-epi-brassinosteroid (24-EBR) on the remediation of cadmium (Cd)-contaminated soil by B. pilosa L. was examined. The results showed:① the efficiency of the remediation in Cd-contaminated soil by B. pilosa L. was effectively enhanced after the spraying of all three kinds of exogenous plant hormones with appropriate concentrations. The spraying of the three exogenous plant hormones could promote the cadmium concentration in the leaves of B. pilosa L. to increase by 4.21%, 31.79%, and 14.89%; promote the translocation factor (TF) to increase by 9.67%, 18.83%, and 17.85%; promote the phytoextraction rates (PR) to increase by 15.36%, 32.33%, and 64.38%, respectively. ② The growth of B. pilosa L. was significantly promoted after the spraying of the three kinds of exogenous plant hormones with appropriate concentrations. The spraying of the three exogenous plant hormones could promote plant growth under cadmium stress, and the dry weight of the plant root, stem, and leaf was increased by 37.53%, 74.50%, and 104.02%, respectively. ③ The photosynthesis of B. pilosa L. was significantly enhanced after the spraying of the three kinds of exogenous plant hormones with appropriate concentrations. The chlorophyll concentration of the plant was significantly increased after foliar spraying with plant hormones, and the concentration of chlorophyll a was increased by 79.31%, 92.27%, and 51.12%; the photochemical quenching coefficient (qP) was increased by 11.32%, 89.16%, and 78.43%; and the non-photochemical quenching coefficient (NPQ) was increased by 51.71%, 241.12%, and 27.85%, respectively, after foliar spraying with appropriate concentrations of 6-BA, SA, and 24-EBR. ④ The antioxidant capacity of B. pilosa L. was significantly strengthened after the spraying of the three kinds of exogenous plant hormones with appropriate concentrations. The malondialdehyde (MDA) concentration of the plant was reduced by 62.41%, 68.67%, and 46.76% after the application of 6-BA, SA, and 24-EBR, respectively. Meanwhile, superoxide dismutase (SOD) was increased by 68.33%, 10.28%, and 6.17%, and catalase (CAT) was increased by 31.43%, 37.87%, and 37.31%, respectively. Generally, the spraying of exogenous 6-BA, SA, and 24-EBR with the appropriate concentration under Cd stress could significantly increase the biomass of B. pilosa L. and promote the accumulation of heavy metals in the plant, improve the photosynthetic ability of the plant, reduce the oxidative damage of the plant under heavy metal stress, enhance the antioxidant capacity, and improve the absorption and tolerance of plants to Cd. It also could promote the transfer of Cd from roots to shoots, improve the phytoextraction rates of Cd from the plant, and effectively strengthen the phytoremediation efficiency. Among them, 30 mg·L-1 SA foliar spraying had the best effect.

Assessment of application of ZnO nanoparticles on physiological profile, root architecture and antioxidant potential of Solanum lycopersicum

Plant growth can be impacted by ZnO nanoparticles (ZnO-NPs), in addition to their effects on photosynthesis and seed germination. The degree to which nanoparticles (NPs) enhance or inhibit shoot and root growth can vary depending on the specific type of NPs and their concentrations. This research aimed to explore the effects of ZnO-NPs on tomato plants (Solanum lycopersicum L.). The study measured the growth of the plants, their photosynthetic abilities, chlorophyll, physiology responses, antioxidant activities in 24-day-old plants. The results indicated that ZnO-NPs applications improved germination percentage (30.7%), shoot length (47.6%) and root length (33.1%) of the tomato plants, particularly at 75 μg/mL, and enhanced chlorophyll content in a manner proportional to the concentration. Moreover, in current research, it has been found that ZnO-NPs applications improved antioxidant response, and production of antioxidant enzymes. ZnO-NPs also had a beneficial impact on various root parameters including number of root tips (29.6%), number of branching points (16.6%), average diameter (46.2%), branching frequency (26.6%), total root length (33.1%), network area (26.3%), surface area (24.0%), perimeter (22.0%) and root volume (25.2%). Above 75 μg/mL, a reduction in all of them have been noticed, which indicates that concentrations of ZNPs above 75 μg/mL are harmful to tomato plants. Moreover, ZNPs appear to stimulate the transcription of various genes which have antioxidant activities, implying that they may bolster the plant's defense mechanism by enhancing antioxidant enzyme activity. According to our best knowledge, this is a novel aspect to study of impact of ZnO-NPs on root architecture of Solanum lycopersicum L.

Harnessing the Genetic Basis of Sorghum Biomass-Related Traits to Facilitate Bioenergy Applications.

The extensive use of fossil fuels and global climate change have raised ever-increasing attention to sustainable development, global food security and the replacement of fossil fuels by renewable energy. Several C4 monocot grasses have excellent photosynthetic ability, stress tolerance and may rapidly produce biomass in marginal lands with low agronomic inputs, thus representing an important source of bioenergy. Among these grasses, Sorghum bicolor has been recognized as not only a promising bioenergy crop but also a research model due to its diploidy, simple genome, genetic diversity and clear orthologous relationship with other grass genomes, allowing sorghum research to be easily translated to other grasses. Although sorghum molecular genetic studies have lagged far behind those of major crops (e.g., rice and maize), recent advances have been made in a number of biomass-related traits to dissect the genetic loci and candidate genes, and to discover the functions of key genes. However, molecular and/or targeted breeding toward biomass-related traits in sorghum have not fully benefited from these pieces of genetic knowledge. Thus, to facilitate the breeding and bioenergy applications of sorghum, this perspective summarizes the bioenergy applications of different types of sorghum and outlines the genetic control of the biomass-related traits, ranging from flowering/maturity, plant height, internode morphological traits and metabolic compositions. In particular, we describe the dynamic changes of carbohydrate metabolism in sorghum internodes and highlight the molecular regulators involved in the different stages of internode carbohydrate metabolism, which affects the bioenergy utilization of sorghum biomass. We argue the way forward is to further enhance our understanding of the genetic mechanisms of these biomass-related traits with new technologies, which will lead to future directions toward tailored designing sorghum biomass traits suitable for different bioenergy applications.

Understanding the effect of heat stress during seed filling on nutritional composition and seed yield in chickpea (Cicer arietinum L.)

Increasing temperature affects all food crops, thereby reducing their yield potential. Chickpea is a cool-season food legume vital for its nutritive value, but it is sensitive to high temperatures (> 32/20 °C maximum/minimum) during its reproductive and seed-filling stages. This study evaluated the effects of heat stress on yield and qualitative traits of chickpea seeds in a controlled environment. Chickpea genotypes differing in heat sensitivity [two heat-tolerant (HT) and two heat-sensitive (HS)] were raised in pots, initially in an outdoor environment (average 23.5/9.9 °C maximum/minimum), until the beginning of pod set (107–110 days after sowing). At this stage, the plants were moved to a controlled environment in the growth chamber to impose heat stress (32/20 °C) at the seed-filling stage, while maintaining a set of control plants at 25/15 °C. The leaves of heat-stressed plants of the HT and HS genotypes showed considerable membrane damage, altered stomatal conductance, and reduced leaf water content, chlorophyll content, chlorophyll fluorescence, and photosynthetic ability (RuBisCo, sucrose phosphate synthase, and sucrose activities) relative to their corresponding controls. Seed filling duration and seed rate drastically decreased in heat-stressed plants of the HT and HS genotypes, severely reducing seed weight plant–1 and single seed weight, especially in the HS genotypes. Yield-related traits, such as pod number, seed number, and harvest index, noticeably decreased in heat-stressed plants and more so in the HS genotypes. Seed components, such as starch, proteins, fats, minerals (Ca, P, and Fe), and storage proteins (albumin, globulins, glutelin, and prolamins), drastically declined, resulting in poor-quality seeds, particularly in the HS genotypes. These findings revealed that heat stress significantly reduced leaf sucrose production, affecting the accumulation of various seed constituents, and leading to poor nutritional quality. The HT genotypes were less affected than the HS genotypes because of the greater stability of their leaf water status and photosynthetic ability, contributing to better yield and seed quality traits in a heat-stressed environment.

High light and temperature enhancing astaxanthin production in Microcystis aeruginosa—Providing a potential thought for controlling cyanobacterial blooms through resource utilization

Artificial salvage is the common method to control cyanobacterial blooms that easily outbreak in summer, but the salvaged cyanobacteria are not effectively utilized. Microcystis aeruginosa is a typical species in cyanobacterial blooms and can accumulate astaxanthin. To promote cyanobacterial blooms control through producing astaxanthin as resource utilization manner, the algal cell growth, photosynthetic abilities, astaxanthin and its precursor levels as well as related gene expression in M. aeruginosa was investigated under high light (HL) and high temperature (HT), the typical conditions in summer. Under HL and HT conditions, M. aeruginosa cell growth and photosynthetic abilities were reduced, due to the declined chlorophyll content and down-regulated photosynthesis-related gene expression. During the 5 days, the astaxanthin content was gradually increased with elevating the light intensity and temperature, reaching the maximum level under HL at 1000 μmol·m−2·s−1 and HT at 35 °C. However, the precursor (β-carotene and zeaxanthin) levels were gradually decreased. This indicated that HL and HT can promote astaxanthin generation and the precursor transformation, as the expression of the genes related with methylerythritol-4-phosphate pathway and astaxanthin formation was up-regulated. Therefore, summer weather can promote astaxanthin accumulation in cyanobacteria by raising related gene expression. During cyanobacterial blooms in summer, their enormous biomass and high astaxanthin level provide a potential for astaxanthin production, while the cyanobacteria salvaged in other seasons can be cultured under HL (1000 μmol·m−2·s−1) and HT (35 °C) conditions to improve astaxanthin content for extracting the high-value compound, which are beneficial to promoting cyanobacterial blooms control through salvage and resource utilization.

Drought tolerance in dipterocarp species improved through interspecific hybridization in a tropical rainforest

Gene transfer through interspecific hybridization can enhance functions such as growth performance, although its role in the ecophysiological functions of tropical tree species remains unclear. Hybrid seedlings of genus Shorea (Dipterocarpaceae), which dominates the canopy layer, are found in fragmented tropical rainforests in Southeast Asia. To elucidate changes in dipterocarp environmental adaptability due to hybridization, we studied the ecophysiological traits of dipterocarp seedlings including leaf morphology, photosynthesis, and drought tolerance in two parent species (Shorea curtisii and Shorea leprosula) and their hybrids, including F1 and backcross hybrids. Then, we induced drought stress to investigate drought tolerance in these seedlings. Photosynthetic ability was higher in S. leprosula than in S. curtisii, with the F1 and backcross hybrids showing intermediate characteristics. By contrast, drought tolerance, as indicated by stem hydraulic safety, cuticle thickness, and leaf mass per area, was higher in S. curtisii, lower in S. leprosula, and intermediate in their hybrids. The leaf turgor loss point decreased in S. curtisii due to osmotic adjustment under drought conditions, which led to lower predawn leaf water potential and higher water absorption ability from drier soil. By contrast, these changes were smaller and drought tolerance was weaker in S. leprosula. The hybrids including backcrosses had higher drought tolerance than S. leprosula, suggesting that gene transfer through introgression may facilitate the acquisition of drought tolerance. Although increased drought stress due to climate change and forest degradation are likely to limit seedling regeneration in S. leprosula, drought-tolerant genes obtained through hybridization with S. curtisii may contribute to its survival.

Sustainable production of photosynthetic isobutanol and 3-methyl-1-butanol in the cyanobacterium Synechocystis sp. PCC 6803

BackgroundCyanobacteria are emerging as green cell factories for sustainable biofuel and chemical production, due to their photosynthetic ability to use solar energy, carbon dioxide and water in a direct process. The model cyanobacterial strain Synechocystis sp. PCC 6803 has been engineered for the isobutanol and 3-methyl-1-butanol production by introducing a synthetic 2-keto acid pathway. However, the achieved productions still remained low. In the present study, diverse metabolic engineering strategies were implemented in Synechocystis sp. PCC 6803 for further enhanced photosynthetic isobutanol and 3-methyl-1-butanol production.ResultsLong-term cultivation was performed on two selected strains resulting in maximum cumulative isobutanol and 3-methyl-1-butanol titers of 1247 mg L−1 and 389 mg L−1, on day 58 and day 48, respectively. Novel Synechocystis strain integrated with a native 2-keto acid pathway was generated and showed a production of 98 mg isobutanol L−1 in short-term screening experiments. Enhanced isobutanol and 3-methyl-1-butanol production was observed when increasing the kivdS286T copy number from three to four. Isobutanol and 3-methyl-1-butanol production was effectively improved when overexpressing selected genes of the central carbon metabolism. Identified genes are potential metabolic engineering targets to further enhance productivity of pyruvate-derived bioproducts in cyanobacteria.ConclusionsEnhanced isobutanol and 3-methyl-1-butanol production was successfully achieved in Synechocystis sp. PCC 6803 strains through diverse metabolic engineering strategies. The maximum cumulative isobutanol and 3-methyl-1-butanol titers, 1247 mg L−1 and 389 mg L−1, respectively, represent the current highest value reported. The significantly enhanced isobutanol and 3-methyl-1-butanol production in this study further pave the way for an industrial application of photosynthetic cyanobacteria-based biofuel and chemical synthesis from CO2.

Melatonin Reverses High-Temperature-Stress-Inhibited Photosynthesis in the Presence of Excess Sulfur by Modulating Ethylene Sensitivity in Mustard.

Melatonin is a pleiotropic, nontoxic, regulatory biomolecule with various functions in abiotic stress tolerance. It reverses the adverse effect of heat stress on photosynthesis in plants and helps with sulfur (S) assimilation. Our research objective aimed to find the influence of melatonin, along with excess sulfur (2 mM SO42-), in reversing heat stress's impacts on the photosynthetic ability of the mustard (Brassica juncea L.) cultivar SS2, a cultivar with low ATP-sulfurylase activity and a low sulfate transport index (STI). Further, we aimed to substantiate that the effect was a result of ethylene modulation. Melatonin in the presence of excess-S (S) increased S-assimilation and the STI by increasing the ATP-sulfurylase (ATP-S) and serine acetyltransferase (SAT) activity of SS2, and it enhanced the content of cysteine (Cys) and methionine (Met). Under heat stress, melatonin increased S-assimilation and diverted Cys towards the synthesis of more reduced glutathione (GSH), utilizing excess-S at the expense of less methionine and ethylene and resulting in plants' reduced sensitivity to stress ethylene. The treatment with melatonin plus excess-S increased antioxidant enzyme activity, photosynthetic-S use efficiency (p-SUE), Rubisco activity, photosynthesis, and growth under heat stress. Further, plants receiving melatonin and excess-S in the presence of norbornadiene (NBD; an ethylene action inhibitor) under heat stress showed an inhibited STI and lower photosynthesis and growth. This suggested that ethylene was involved in the melatonin-mediated heat stress reversal effects on photosynthesis in plants. The interaction mechanism between melatonin and ethylene is still elusive. This study provides avenues to explore the melatonin-ethylene-S interaction for heat stress tolerance in plants.

Response of needle photosynthetic and anatomical characteristics of naturally regenerated Pinus koraiensis seedlings to different canopy densities.

We took 5-year-old Pinus koraiensis seedlings under natural secondary forests with canopy densities of 0.2-0.3, 0.4-0.6, and 0.7-0.9 at Laoshan Plantation Experimental Station in Maoershan Experimental Forest Farm of Northeast Forestry University as monitor object, and P. koraiensis seedlings under full-light environment as control (CK), to investigate the photosynthetic characteristics and the anatomical structure of P. koraiensis needles in response to the changes of canopy densities. The results showed that the height and diameter of P. koraiensis seedlings tended to decrease while specific leaf area increased with the increases of canopy densities. The total biomass of P. koraiensis seedlings under different canopy densities ranked in an order of 0.4-0.6＞CK＞0.7-0.9＞0.2-0.3. Photosynthetically active radiation (PAR) was significantly and positively correlated with leaf biomass, stem biomass, and root biomass. The net photosynthetic rate, transpiration rate, and intercellular CO2 concentration of P. koraiensis seedlings showed a decreasing trend with the increases of canopy densities, while the stomatal conductance showed an increasing trend. Net photosynthetic rate and chlorophyll a/b showed a significant positive correlation with PAR. Stomatal density showed a gradual decreasing trend with the increases of canopy densities, and the needle cross-sectional area, mesophyll tissue area, xylem area, and phloem area of P. koraiensis seedlings under canopy density 0.4-0.6 were significantly higher than those in other treatments. P. koraiensis seedlings with stronger photosynthetic abilities and higher needle anatomy parameters under canopy density 0.4-0.6, and were able to maintain strong competitiveness in this habitat. Those results indicated that 5-year-old P. koraiensis seedlings need certain shading environment.

Gene co-expression networks unravel the molecular responses of freshwater hydrophytes to combined stress of salinity and cadmium

Salinization in freshwater lakes is becoming a serious global environmental problem, especially in lakes of plateaus such as south-western plateau of China. However, limited information is available about the molecular response of freshwater hydrophytes to salinity under multiple stress. In the present study, a weighted gene co-expression network (WGCNA) was used to identify the modules of co-expressed genes in the physiological and biochemical indicators of Pistia stratiotes to determine its molecular response to salinity (NaCl) alone and when combined with cadmium (Cd). The physiological and biochemical indicators showed that P. stratiotes improved its salt tolerance by enhancing photosynthetic abilities, reducing oxidative stress, and inducing osmoprotectant generation. Morever, addition of NaCl reduced the Cd accumulation in P. stratiotes. Transcriptome and WGCNA analysis revealed that the pathways of alpha-linolenic acid metabolism, ribosomal, flavonoid biosynthesis, and phenylpropanoid biosynthesis were significantly enriched in both treatments. Genes associated with photosynthesis-antenna proteins, nitrogen metabolism, and the acid cycle pathways were only expressed under salinity stress alone, while the proteasome pathway was only significantly enriched in the combined salinity and Cd treatment. Our findings provide novel insights into the effects of salinization on aquatic plants in freshwater ecosystems and the management of aquatic ecosystems under global change.

CsSE59 Encoding Invertase/Pectin Methyl Esterase Inhibitor Is a Candidate Gene Conferring the Virescent True Leaf Phenotype in Cucumber

Leaf color mutants are the ideal materials to study the regulation mechanisms of chlorophyll biosynthesis and chloroplast development or as markers for crop breeding. In this study, we identified a virescent true leaf mutant se59 from the ethyl methane sulfonate (EMS)-induced mutant lines of cucumber (Cucumis sativus L.). The se59 mutant showed normal cotyledons, but the true leaf displays light green at early growth stage, which can recover normal green later. The se59 locus was controlled by a single recessive nuclear gene. The grana stacking in the chloroplasts of se59 decreased significantly, and both the photosynthetic ability and the photosynthetic pigment contents of the se59 were significantly lower than those of wild type. The results of BSA-seq and genotyping showed that an Invertase/Pectin Methyl Esterase Inhibitor (INV/PMEI) protein encoded by CsSE59 is a candidate gene for the virescent true leaf mutant. The expression level of CsSE59 in stem, leaf and root is high. Based on the transcriptome analysis of the first true leaf of se59 mutant, the expression levels of 17 leaf color related genes changed significantly, suggesting CsSE59 may regulate virescent true leaf by interacting with some of these genes in cucumber. The identification of CsSE59 is helpful to clarify the role of INV/PMEI in chloroplast development and to understand the mechanisms of leaf color variation in cucumber.

Difference between Day and Night Temperature (DIF) and Light Intensity Affect Growth and Photosynthetic Characteristics of Panax ginseng Meyer Sprouts.

Panax ginseng sprouts (PGS) have the advantage of requiring short-term cultivation while maintaining higher ginsenoside contents than traditional ginseng seedlings. It is feasible to improve their yield capacity by manipulating physical factors such as temperature and light. This study therefore investigated the effects of the DIF (difference between day and night temperature) and LI (light intensity) on the growth and photosynthetic characteristics of PGS. To this end, four DIF treatments (18/22 °C, 20/20 °C, 22/22 °C, 22/18 °C), corresponding to two LI regimes (20 PPFD, 200 PPFD), were applied on one-year-old ginseng rootlets in closed-type plant production systems (CPPSs). The PGS had distinctly different responses to the eight treatments. In particular, we found that negative DIF considerably hampered the growth and development of roots, shoots, leaves, and photosynthesis, regardless of the LI considered. The PGS treated with 20/20 °C combined with 20 PPFD displayed the best root growth, shoot development, leaf area, as well as optimal photosynthetic ability. On the other hand, we further showed that the root growth rate was positively correlated with the stem diameter, leaf traits, and photosynthetic ability, whereas it was negatively correlated with the petiole length, stem length, and shoot length. Collectively, 20/20 °C combined with 20 PPFD was the optimal condition in the current study, and may be regarded as a successful strategy for large-scale productions of PGS.

Impact of mercury on photosynthetic performance of Lemna minor: a chlorophyll fluorescence analysis

The purpose of this study was to evaluate the effectiveness of chlorophyll fluorescence analysis in detecting the effects of mercury (Hg) treatment in duckweed species Lemna minor. The results showed that Hg treatment (ranging from 0.0 to 0.4 µM) significantly impacted the plant's photosynthetic ability, with a decrease in variable chlorophyll fluorescence, energy fluxes, density of reaction centers, and performance index. Complete inhibition of electron transport was observed in plants treated with high Hg concentrations, and the quantum yield of primary photochemistry and the ratio of dissipated energy to absorption both decreased with increasing Hg concentrations. Performance Index (PI) was significantly affected by the Hg concentrations, reaching zero in plants treated with the highest Hg concentration. Overall, JIP analysis was found to be an effective tool for detecting deleterious effects of Hg in plants.

Algae: The Reservoir of Bioethanol

Overuse of non-renewable fossil fuels due to the population explosion urges us to focus on renewable fuels such as bioethanol. It is a well-known fact that ethanol is useful as a blending product with common fuels such as petrol and diesel. This reduces the cost besides bringing down environmental pollution. Apart from chemical methods, bioethanol is generated from photosynthetic plants including algae, plant-based products, microbial organisms and their waste. Specifically, the production of ethanol from microalgal sources has been an attractive method in recent days. The reason behind using microalgal species is their simple structure with photosynthetic ability. In contrast, certain algal species often go disused in some regions. Hence, the production of ethanol from algal sources is one of the best waste management practices. Moreover, it is easy to improve the biomass in microalgal species by altering the physicochemical conditions such as light, pH, temperature, external supply of nutrients, vitamins, nano-sized particles, gene alterations etc., which will enhance ethanol production. In this review, the methods used for ethanol production are discussed. In addition, the factors involved in algal growth and ethanol production are emphasized. Overall, this review focuses on ethanol production from various algal species. This information will be useful for industrial-level production of ethanol and future renewable energy research.

Maize–soybean relay cropping increases soybean yield synergistically by extending the post-anthesis leaf stay-green period and accelerating grain filling

Relay cropping of Poaceae and Fabaceae promotes high yield and land-use efficiency by allowing a double harvest. However, it is difficult to increase yield synergistically because of the reduced photosynthetic abilities of legume leaves under the shade of graminoids. Leaf photosynthetic capacity in relay cropping systems is associated with ecological niche differentiation and photosynthetic compensation after restoration of normal light. We conducted a field experiment in southwest China in 2020–2021 to evaluate the effects of three cropping patterns: maize–soybean relay cropping (IMS), monoculture maize (MM), and monoculture soybean (SS), and N application levels: no N application (NN:0 kg N ha−1), reduced N (RN: 180 kg N ha−1), and conventional N (CN: 240 kg N ha−1). Compared to monocropping, relay cropping increased the stay-green traits of maize and soybean by 13% and 89%, respectively. Relay cropping prolonged the leaf stay-green duration in the maize and soybean lag phase by almost 4 and 8 days, respectively. Relay cropping maize (IM) increased the leaf area index (LAI) by 79.4% to 88.5% under NN and 55.5% to 148% under RN. Relay cropping soybean (IS) increased the LAI from 115% to 437% at days 40 to 50 after anthesis. IM increased yield by 65.6%. IS increased yield by 9.7%. HI and system yield were at their highest values under RN. In the relay cropping system, reduced N application extended green leaf duration, increased photosynthesis inside the canopy at multiple levels, ultimately increases soybean yield synergistically.

The Synergistic Mechanism of Photosynthesis and Antioxidant Metabolism between the Green and White Tissues of Ananas comosus var. bracteatus Chimeric Leaves.

Ananas comosus var. bracteatus (Ac. bracteatus) is a typical leaf-chimeric ornamental plant. The chimeric leaves are composed of central green photosynthetic tissue (GT) and marginal albino tissue (AT). The mosaic existence of GT and AT makes the chimeric leaves an ideal material for the study of the synergistic mechanism of photosynthesis and antioxidant metabolism. The daily changes in net photosynthetic rate (NPR) and stomatal conductance (SCT) of the leaves indicated the typical crassulacean acid metabolism (CAM) characteristic of Ac. bracteatus. Both the GT and AT of chimeric leaves fixed CO2 during the night and released CO2 from malic acid for photosynthesis during the daytime. The malic acid content and NADPH-ME activity of the AT during the night was significantly higher than that of GT, which suggests that the AT may work as a CO2 pool to store CO2 during the night and supply CO2 for photosynthesis in the GT during the daytime. Furthermore, the soluble sugar content (SSC) in the AT was significantly lower than that of GT, while the starch content (SC) of the AT was apparently higher than that of GT, indicating that AT was inefficient in photosynthesis but may function as a photosynthate sink to help the GT maintain high photosynthesis activity. Additionally, the AT maintained peroxide balance by enhancing the non-enzymatic antioxidant system and antioxidant enzyme system to avoid antioxidant damage. The enzyme activities of reductive ascorbic acid (AsA) and the glutathione (GSH) cycle (except DHAR) and superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were enhanced, apparently to make the AT grow normally. This study indicates that, although the AT of the chimeric leaves was inefficient at photosynthesis because of the lack of chlorophyll, it can cooperate with the GT by working as a CO2 supplier and photosynthate store to enhance the photosynthetic ability of GT to help chimeric plants grow well. Additionally, the AT can avoid peroxide damage caused by the lack of chlorophyll by enhancing the activity of the antioxidant system. The AT plays an active role in the normal growth of the chimeric leaves.